When need to update software or download data to a group of electronic devices, for example, electronic devices in a big organization, the electronic devices generally are coupled to a server which can store data to be download. When all the electronic devices are coupled to the server to download data from the server, a heavy burden will be applied on the server. Moreover, when the electronic devices are coupled to the server through a network, for example, Local Area network (LAN), the network may come to congestion.